In a typical cellular radio network, also referred to as a wireless communication system, User Equipments, also referred to as UEs in the figures, communicate via a Radio Access Network (RAN) to one or more core networks (CNs).
A user equipment is a mobile terminal by which a subscriber can access services offered by an operator's core network.
The user equipments are radio network nodes and may be mobile stations or user equipment units such as mobile telephones, also known as “cellular” telephones, and laptops with wireless capability, and thus may be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with the radio access network.
Each cell in the cellular radio network covers a geographical area. A cell is served by radio base station equipment at a radio base station. That is, the radio base station provides radio coverage in the cell and communicates over an air interface with user equipment units operating on radio frequencies within its range.
A cell from within which the communication between a user equipment and a base station is communicated, is referred to as the “serving cell” for that user equipment.
A radio base station is a radio network node, in some radio networks called “eNB”, “eNodeB”, “NodeB” or “B node”, and will in this document be referred to as a base station (BS), or a radio network node.
In some versions of the radio access network, several base stations are controlled, e.g. via landlines or radio link, by a Radio Network Controller (RNC) which supervises and coordinates various activities of the plural base stations connected thereto. The radio network controller, which also is a radio network node, is also sometimes termed a Base Station Controller (BSC). The radio network controllers are typically connected to one or more core networks.
In LTE-type radio access networks, there is no separate radio network node corresponding to the BSC or RNC, and the base stations themselves, referred to as eNodeB:s comprise extra functionality.
Due to the size and complexity of many radio communication systems, operators today spend considerable effort in planning, configuring, optimizing, and maintaining their wireless access networks. These efforts can consume a great part of their operational expenditures (OPEX).
Today, operators resort to planning tools to dimension and plan their networks according to a specific business strategy. The approach based on planning tools and prediction is, however, not fully accurate. Reasons for the inaccuracies are imperfections in the used geographic data, simplifications and approximations in the applied propagation models, and changes in the environment, e.g. construction or demolition or seasonal effects such as foliage changes. Furthermore, changes in the traffic distribution and user profiles can lead to inaccurate prediction results. The above mentioned shortcomings force operators to continuously optimize their networks using measurements and statistics, and to perform drive or walk tests.
Drive or walk testing provides a picture of the end user, such as a user equipment, perception in the field, and enables the operator to identify locations causing poor performance and their corresponding cause, e.g. incorrect tilt or handover settings. Drive/walk tests are, however, not ideal since only a limited part of the network can be analyzed due to access restrictions and the cost and time involved. Further, only a snapshot in time of the conditions in the field is captured.
A viable method for overcoming these difficulties is to use the user equipments to report the observed service quality along with the locations where the measurements are performed. These user equipment reports may for example be used by a function which continuously monitors the network and estimates the spatial network performance, e.g. coverage and throughput.
For LTE, three different localization methods are foreseen. The first location function is the network-assisted version of Global Navigation Satellite Systems (GNSSs) like the Global Positioning System (GPS) or Galileo. Different GNSSs can be used individually or in combination with other GNSSs. The network assists the UE GNSS receiver by providing assistance data (e.g., visible satellite list, clock corrections, reference positions) to reduce the UE GNSS start-up and acquisition times, to increase the UE GNSS sensitivity, and to allow the UE to consume less handset power than with stand-alone GNSS. The network-assisted GNSS methods rely on signaling between UE GNSS receivers and a continuously operating GNSS reference receiver network which has clear sky visibility of the same GNSS constellation as the assisted UE.
The second localization method is the Observed Time Difference Of Arrival (OTDOA) method. This method utilizes the differences of time measurements of downlink radio signals from at least three eNodeBs along with the knowledge of the geographical coordinates of the measured eNodeBs and their relative downlink timing for calculating the UE position. The relative eNodeB downlink timing can be determined from information about the relation of each eNodeB downlink timing relative a time reference. One such time reference is the absolute time in the network.
The last localization method, the enhanced cell ID positioning method, uses information about the user equipments, information about the serving cell, and the knowledge of the geographical coordinates of the serving eNodeB for estimating the user equipment position. Additional radio resource measurements like the Reference Signal Received Power (RSRP) or the Reference Signal Received Quality (RSRQ) can be used to improve the user equipment location estimate.
According to one solution user equipment reports include position information in which the user equipments report or log radio measurements (e.g., RSRP), and also provide location info if the latter is available in the user equipment at the time of reporting or logging.
One problem with the above mentioned solution is that the user equipment information is reported by the user equipment only if the position information is known at the time the report is transmitted or measurements logged. This means that the user equipment must have GPS enabled or recently used a positioning service relying on e.g. OTDOA. The UEs will typically have GPS enabled during a limited time or will use GPS frequently but over the same area, e.g., highways.
It may also be desirable to obtain a more accurate position estimate than may be provided by the above methods.